This project is designed to explore the role of neural proteinases in the removal of cartilage matrix accompanying bone formation in the growth zones of embryonic limb primordia. The working hypothesis for the proposed studies is that neural proteoglycan degrading enzymes resistant to tissue and serum inhibitors, similar to one secreted by a malignant rat tumor enzyme recently described by us may be involved in the normal process of cartilage removal accompanying endochondral bone formation in the embryo. Preliminary studies in the chick embryo limb indicate the presence of proteoglycan degrading proteinases in the growth zone, one of which may have properties similar to that of the tumor enzyme. 1. By immunolocalization methods using the tumor enzyme as antigen for monoclonal antibodies a search will be made for similar enzymes in the growth zones of embryonic rat long bones and in bone repair tissue in neonatal rats. 2. Developing chick embryo limb, which can provide more tissue for biochemical studies, will be used for isolation, purification and characterization of neutral PG degrading proteinases. 3. Cellular source, regulation and relationship of these enzymes to bone formation and repair will be explored using biochemical and immunological methods well established in this Laboratory. The knowledge gained may be useful in understanding not only normal skeletal development, but also genetic and metabolic abnormalities and bone repair processes.